A rectangular dielectric resonator antenna based on a novel concave ground plane design is presented for wideband applications in this letter. To examine the effect of the concave ground plane on the antenna performance, numerical simulations and experimental investigations were carried out, and a good agreement between the theoretical expectation and the measured results validates the proposed design, which shows that using a concave ground plane instead of a planar ground plane may broaden the impedance bandwidth to 1.4 times. The measured impedance bandwidth of the proposed rectangular DRA achieves about 55% for VSWR les 2, covering the frequency range from 3.28 to 5.77 GHz. Furthermore, this antenna provides a stable radiation pattern with a gain range of 3.7-6.2 dBi in the operating band.